Air in-line sensor for ambulatory drug infusion pump

ABSTRACT

An air in-line sensor  10  for detecting air bubbles in a therapeutic solution flowing through a tube  12  utilizes a unitary type sensor having a channel  16  for receiving the tube  12.  The channel  16  has a tube loading section  18.  A signal emitting member  20  is positioned on one side of the tube  12  and a signal receiving member  22  is positioned on an opposite side of the tube  12.  A first air baffle  24  is positioned between the signal emitting  20  and signal receiving members  22.

DESCRIPTION

[0001] 1. Technical Field

[0002] The present invention relates to an air in-line sensor for use ina medical device and, more particularly, to an air in-line sensordesigned to detect air bubbles in a therapeutic solution flowing througha tube.

[0003] 2. Background of the Invention

[0004] An infusion system for delivering a drug or other liquid into apatient often includes an infusion device that operates to deliver theliquid at an adjustable rate or dosage. Prior art infusion devicesinclude an air detector using an ultrasonic or an optical sensor fordetecting air bubbles in the liquid flowing through a tube. The airdetector is loaded in a part of the tube.

[0005] Two types of the air detectors are known. More specifically, inthe separate type as shown in FIG. 1, a signal emitting member 1 and asignal receiving member 2 of the detector are separate components insuch a structure. The signal emitting member 1 is mounted on astationary unit 3 of a pumping station, while the signal receivingmember 2 is carried by a movable unit 4, such as a door. When the door 4is closed, a channel 5 is defined between an upper surface of signalemitting member 1 of stationary unit 3 and a lower surface of signalreceiving member 2 of movable unit 4, into which a tube 6 isaccommodated. Accordingly, when movable unit 4 is closed while tube 6 isloaded into an upper recess 7 defined in signal emitting member 1 ofstationary unit 3, tube 6 is deformed into a flattened configurationwithin channel 6 to provide an enlarged surface area in contact withsignal emitting and receiving members 1 and 2.

[0006] On the other hand, in the unitary type of the air detector asshown in FIGS. 2 and 3, a tube-receiving groove 8 is defined instationary unit 3. Both signal emitting and receiving members 1 and 2are embedded in opposing walls of groove 8. The unitary type is mainlyused for detecting relatively short air bubbles and therefore the lengthof tube-receiving groove 8 is relatively short, exerting less resistancein contact between the groove and the tube. Accordingly, the tube may befitted into groove 8 by pushing with one's fingers.

[0007] In the above-described separate type, it is difficult to maintaina constant, specific distance between the signal emitting and receivingmembers so as to stabilize the performance of the detector, because theseparate type sensor system has more tolerances than a unitary typesystem. When more tolerances are involved, distance control between thesignal emitting and receiving members becomes more difficult.

[0008] Nuisance alarms result when a pump alarm is activated when air isnot present in the line. As a result, air sensors are often deactivatedin the pump's configuration. Accordingly, the pump would not be able todetect the presence of air in the line. Moreover, nondetection of actualair in the tubing line occurs in many prior art infusion devices becausethe ultrasonic signal is not fully transmitted through the tube. Forexample, an ultrasonic signal may work its way around the bottom of thechannel and trick the pump mechanism into believing that liquid is inthe line when, in fact, air is in the line. This nondetection or “shortcircuit” is undesirable.

[0009] Some unitary type air sensors have included a pocket underneaththe channel to block the ultrasonic signal, and thus, prevent theultrasonic signal from circumventing the correct path through the tubingset. However, these pockets can allow dirt and cleaning solutions tobuild up, which prevents the sensor from working properly. If the pocketbecame filled with liquid, the ultrasonic signal may travel around thechannel even when air is present in the tubing line.

[0010] Moreover, some unitary type air sensor systems do not maintainoptimal contact between the tube and the channel. For example, if a flatclosure member surface is utilized to push the tube into a V-shaped,upper section of the channel, the tube may become dislodged from thechannel by rotational or rolling displacement of the tube. Additionally,the tube may flatten or collapse disproportionately, causing poorcoupling between the tube and the channel.

[0011] U.S. Pat. No. 5,102,392, owned by Assignee of the presentinvention, discloses an air detector for use in infusion pumps (seeFIGS. 2 and 3). The air detector utilizes a unitary type sensor fordetecting air bubbles in the tube. The upper section of the groove has afirst side wall which tapers upwardly and outwardly from the tube fixingsection and a second side wall is perpendicular to the base of thegroove along the length of the tube fixing section. When the door isclosed after the tube is loaded in the groove, the tube abutting memberforces the tube against the second side wall and into final position.

[0012] The present invention is provided to solve these and otherproblems.

SUMMARY OF THE INVENTION

[0013] The present invention provides an air in-line sensor fordetecting air bubbles in a therapeutic solution flowing through a tube.

[0014] According to one aspect of the present invention, the sensor hasa channel for receiving the tube having a tube loading section. Thesensor further has a signal emitting member positioned on one side ofthe tube and a signal receiving member positioned on an opposite side ofthe tube. A first air baffle is positioned between the signal emittingmember and the signal receiving member.

[0015] According to another aspect of the invention, the sensor has afirst lead-in section defined by an upper portion of a first sidewall ofthe channel. The first lead-in section tapers upwardly and outwardlyfrom an intermediate portion of the first sidewall to the upper portionof the first sidewall.

[0016] According to a further aspect of the invention, the sensor has asecond lead-in section positioned opposite the first lead-in section.The second lead-in section is defined by an upper portion of a secondsidewall of the channel, and the second lead-in section tapers upwardlyand outwardly from an intermediate portion of the second sidewall to theupper portion of the second sidewall.

[0017] According to a further aspect of the invention, the sensor has asecond air baffle positioned between the signal emitting and the signalreceiving members.

[0018] According to yet another aspect of the invention, an air in-linesensor is provided for detecting air bubbles in a therapeutic solutionflowing through a tube. The sensor has a channel for receiving the tubehaving a tube loading section. Preferably, the tube has a first lead-insection. The tube loader has a stationary section and a movable sectionhingedly connected to the stationary section. The movable section has ablade having a radius of curvature for positioning the tube in the tubeloading section. Preferably, a signal emitting member is positioned onone side of the tube and a signal receiving member is positioned on anopposite side of the tube.

[0019] According to a further aspect of the invention, an air in-linesensor system is disclosed for detecting air bubbles in a therapeuticsolution flowing through a tube located in a pumping mechanism. The tubeextends from a supply bag of the therapeutic solution to a patientthrough the system. The system has a channel for receiving the tubehaving a first lead-in section, and a tube loading section. A signalemitting member is positioned on one side of the tube and a signalreceiving member is positioned on an opposite side of the tube. A firstair baffle is positioned between the signal emitting member and thesignal receiving member. Moreover, the tube loader has a stationarysection and a movable section hingedly connected to the stationarysection. The movable section has a blade having a radius of curvaturefor positioning the tube in the tube loading section.

[0020] According to yet another aspect of the invention, a method isdisclosed for loading a tube into a channel of a medical pump.Preferably, the channel is provided having a first lead-in section and atube loading section. The channel is also provided having a signalemitting member positioned on one side of the tube and a signalreceiving member positioned on an opposite side of the tube. A tubeloader is provided having a stationary section and a movable section.The movable section has a blade having a radius of curvature. The tubeis positioned proximate the channel. The blade is placed in contact withthe tube, and the blade is then moved until the tube is positionedwithin the tube loading section.

[0021] Other features and advantages of the invention will be apparentfrom the following specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To understand the present invention, it will now be described byway of example, with reference to the accompanying drawings in which:

[0023]FIG. 1 is a schematic front elevational view of a prior art airin-line sensor of the separate type;

[0024]FIG. 2 is a schematic front elevational view of a prior art airin-line sensor of the unitary type;

[0025]FIG. 3 is cross-sectional view of the prior art air in-line sensorof FIG. 2, showing the loading process of a tube;

[0026]FIG. 4 is a perspective view of a tube loader according to apreferred aspect of the present invention;

[0027]FIG. 5 is a schematic front elevational view of an air in-linesensor according to a preferred aspect of the present invention;

[0028]FIG. 6 is a cross-sectional view of the air in-line sensor of FIG.5, showing the loading process of a tube; and

[0029]FIG. 7 is another cross-sectional view of the air in-line sensorof FIG. 5, showing the loading process of a tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] While this invention is susceptible of embodiments in manydifferent forms, there is shown in the drawings and will herein bedescribed in detail preferred embodiments of the invention with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the broad aspect of the invention to the embodimentsillustrated.

[0031] Referring now in detail to the Figures, FIGS. 5-7 illustrate anair in-line sensor 10 for detecting air bubbles in a therapeuticsolution flowing through a tube 12 located in a pumping mechanism 14(see FIG. 4). Tube 12 extends from a supply bag of the therapeuticsolution to a patient through sensor 10. Sensor 10 has a channel 16 forreceiving tube 12 and a tube loading section 18. Sensor 10 also has asignal emitting member 20 positioned on one side of tube 12 and a signalreceiving member 22 positioned on an opposite side of tube 12. Further,sensor 10 has a first air baffle 24 positioned between signal emittingmember 20 and signal receiving member 22 to prevent the ultrasonicsignal from traveling around tube 12.

[0032] Preferably, pumping mechanism 14 is a peristaltic pump, a rollerpump, an expulsor pump, a finger pump or a piston cassette pump. Pumpingmechanism 14 has a stationary section 26 and a movable section 28hingedly connected to stationary section 26. As shown in FIG. 5, movablesection 28 is pivotable about its axis in a direction indicated by anarrow to close and open stationary section 26.

[0033] Movable section 28 has a blade 32 having a radius of curvature 34for positioning tube 12 in pumping mechanism 14. Blade 32 pushes tube 12into the proper position within channel 16. In a preferred aspect of theinvention, channel 16 is U-shaped, and has substantially square cornershaving only a slight radius where base 36 meets first and secondsidewalls 38 and 40, respectively. As shown in FIG. 6, the width 42 ofchannel 16 is smaller than outer diameter 44 of tube 12. This provides alarge contact area between tube 12 and first and second sidewalls 38 and40, respectively.

[0034] Channel 16 has a first lead-in section 46 and a second lead-insection 48 to allow tube 12 to be easily loaded into pumping mechanism14. Each of the first and second lead-in sections 46 and 48,respectively, includes a V-radius and a channel draft for moldingpurposes. Channel 16 has a first lead-in section 46 forming the upperportion of a first sidewall 38 of channel 16. First lead-in section 46tapers upwardly and outwardly from an intermediate portion 50 of firstsidewall 38 to upper portion 52 of first sidewall 38.

[0035] In a preferred aspect of the invention, channel 16 has a secondlead-in section 48 positioned opposite first lead-in section 46. Secondlead-in section 48 forms the upper portion of a second sidewall 40 ofchannel 16. Similar to first lead-in section 46, second lead-in section48 tapers upwardly and outwardly from an intermediate portion 54 ofsecond sidewall 40 to the upper portion 56 of second sidewall 40.

[0036] As shown in FIGS. 6 and 7, blade 32 has a radius of curvaturesubstantially identical to the radius of curvature of tube 12 tomaximize coupling of tube 12 and first and second sidewalls 38 and 40 ofchannel 16. The curved blade allows tube 12 to be pushed down intochannel 16 with a maximum amount of force imparted on first and secondsidewalls 38 and 40, respectively, without distorting tube 12. Thepressure exerted on tube 12 causes the sides of tube 12 to expandhorizontally and push against first and second sidewalls 38 and 40,respectively. Thus, tube 12 is deformed from a circular configurationinto an oval configuration.

[0037] The greater the force of the sides of tube 12 on first and secondsidewalls 38 and 40, respectively, and the greater the contact area oftube 12 and first and second sidewalls 38 and 40, the greater thecoupling between tube 12 and channel 16, and thus, the greater thetransmission of the ultrasonic signal through tube 12. The highercoupling force increases the performance of air sensor 10.

[0038] An electronic circuit drives signal emitting member 20 whichprojects ultrasonic energy across channel 16, tube 12 and the tubecontents. Signal receiving member 22 acts as a receiver. The strength ofthe ultrasonic signal passing through tube 12 is highest when liquid ispresent in tube 12. Conversely, the strength of the ultrasonic signal islowest when air is present in tube 12. The electrical circuit comparesthe strength of the detected signal and decides whether there is air orliquid in tube 12, and thus, whether to sound an air in-line alarm. Whenair passes through tube 12, and thus, the transmission path, theultrasonic energy is interrupted or decreased. Accordingly, theelectrical circuit will output five (5) volts if liquid is present intube 12, and the electrical circuit will output zero (0) volts if air ispresent in tube 12.

[0039] In a preferred aspect of the invention, sensor 10 has a secondair baffle 58 positioned between signal emitting member 20 and signalreceiving member 22. Second air baffle 58 is positioned opposite firstair baffle 24, which prevents the ultrasonic signal from travelingaround tube 12. First air baffle 24 weakens the ultrasonic signaltraveling through tube 12, and thus, prevents a “short circuit” whenhigh coupling forces are present between tube 12 and first and secondsidewalls 38 and 40 and base 36.

[0040] As shown in FIG. 7, the center of signal emitting and receivingmembers 20 and 22 and the center of tube 12 are co-linear and parallelto channel 16 when tube 12 is positioned within channel 16. Channel 16is dimensioned to allow these respective centers to align when tube 12is forced into channel 16 and to reduce manufacturing error. Properalign increases the strength of the signal transmitted through tube 12.

[0041] The width of channel 16 is selected in conjunction with thedimensions of tube 12 to optimize the performance of air sensor 10.Preferably, channel 16 is made of an engineering resin, such as ABSplastic, and has a width of about 0.075 inches at its base. Preferably,the outer diameter of tube 12 is about 0.083 inches, and the innerdiameter is 0.03 inches. The thickness of the U-channel material betweentube 12 and the signal emitting and signal receiving members 20 and 22,respectively, is critical, and, preferably, is 0.027 inches. TheU-channel wall surface finish was also optimized to increase thecoupling between the tubing set and the plastic U-channel walls.Preferably, the U-channel wall is made of a continuous plastic that isfree of voids, glass and fillers.

[0042] In another aspect of the invention, an air in-line sensor 10 isprovided for detecting air bubbles in a therapeutic solution flowingthrough tube 12. Sensor 10 has means for emitting an ultrasonic signalthrough tube 12. Preferably, the means for emitting is a transducer,such as signal emitting member 20. Sensor 10 also has means fordetecting the ultrasonic signal emitted through tube 12. Preferably, themeans for detecting is a transducer, such as signal receiving member 22.

[0043] Sensor 10 further has means for preventing the ultrasonic signalfrom traveling around tube 10. Preferably, the means for preventingemploys two air baffles, such as first air baffle 24 and second airbaffle 58. Air baffles 24 and 58 are positioned between signal emittingmember 20 and signal receiving member 22. Sensor 10 also has means formeasuring the strength of the ultrasonic signal emitted through tube 12.Preferably, the means for measuring is an electrical circuit. Moreover,sensor 10 has means for comparing the strength of the ultrasonic signalto a preset voltage value. Preferably, the means for comparing employs avoltage comparator.

[0044] Sensor 10 further has means for outputting a preset, maximumvalue if liquid is present in tube 12 and a preset, minimum value if airis present in tube 12. Preferably, the electrical circuit will outputfive (5) volts if liquid is present in tube 12, and the electricalcircuit will output zero (0) volts if air is present in tube 12. Forexample, the voltage comparator is set at 2.5 volts. A signal above 2.5volts would cause the comparator to output 5 volts, and thus, indicatethat liquid is present in tube 12. Conversely, a signal below 2.5 voltswould cause the comparator to output 0 volts, and thus, indicate thatair is present in tube 12. If air is present in tube 12, sensor 10sounds an air in-line alarm.

[0045] A method is disclosed for loading tube 12 into channel 16.Preferably, channel 12 has first lead-in section 46 and tube loadingsection 18. Signal emitting member 20 is positioned on one side of tube12 and signal receiving member 22 is positioned on an opposite side oftube 12. Pumping mechanism 14 is provided having stationary section 26and movable section 28. Movable section 28 has blade 32 having radius ofcurvature 34. Tube 12 is positioned in channel 16, and blade 32 isplaced in contact with tube 12. When movable section 28 is closed, blade32 positions tube 12 in tube loading section 18.

[0046] While the specific embodiments have been illustrated anddescribed, numerous modifications come to mind without significantlydeparting from the spirit of the invention, and the scope of protectionis only limited by the scope of the accompanying claims.

We claim:
 1. An air in-line sensor for detecting air bubbles in atherapeutic solution flowing through a tube, the sensor comprising: achannel for receiving the tube having a tube loading section; a signalemitting member positioned on one side of the tube and a signalreceiving member positioned on an opposite side of the tube; and, afirst air baffle positioned between the signal emitting member and thesignal receiving member.
 2. The sensor of claim 1 further comprising afirst lead-in section.
 3. The sensor of claim 2 wherein the firstlead-in section comprises an upper portion of a first sidewall of thechannel, the first lead-in section tapers upwardly and outwardly from anintermediate portion of the first sidewall to the upper portion of thefirst sidewall.
 4. The sensor of claim 1 wherein the first air baffleprevents an ultrasonic signal from traveling around the tube.
 5. Thesensor of claim 1 further comprising a second air baffle.
 6. The sensorof claim 5 wherein the second air baffle is positioned between thesignal emitting member and the signal receiving member.
 7. The sensor ofclaim 6 wherein the second air baffle prevents an ultrasonic signal fromtraveling around the tube.
 8. The sensor of claim 1 further comprising asecond lead-in section positioned opposite the first lead-in section. 9.The sensor of claim 8 wherein the second lead-in section comprises anupper portion of a second sidewall of the channel, the second lead-insection tapers upwardly and outwardly from an intermediate portion ofthe second sidewall to the upper portion of the second sidewall.
 10. Anair in-line sensor for detecting air bubbles in a therapeutic solutionflowing through a tube, the sensor comprising: a channel for receivingthe tube having a first lead-in section, and a tube loading section; asignal emitting member positioned on one side of the tube and a signalreceiving member positioned on an opposite side of the tube; and, afirst air baffle positioned between the signal emitting member and thesignal receiving member.
 11. The sensor of claim 10 wherein the firstlead-in section comprises an upper portion of a first sidewall of thechannel, the first lead-in section tapers upwardly and outwardly from anintermediate portion of the first sidewall to the upper portion of thefirst sidewall.
 12. The sensor of claim 10 wherein the first air baffleprevents an ultrasonic signal from traveling around the tube.
 13. Thesensor of claim 10 further comprising a second air baffle.
 14. Thesensor of claim 13 wherein the second air baffle is positioned betweenthe signal emitting member and the signal receiving member.
 15. Thesensor of claim 14 wherein the second air baffle prevents an ultrasonicsignal from traveling around the tube.
 16. The sensor of claim 10further comprising a second lead-in section positioned opposite thefirst lead-in section.
 17. The sensor of claim 16 wherein the secondlead-in section comprises an upper portion of a second sidewall of thechannel, the second lead-in section tapers upwardly and outwardly froman intermediate portion of the second sidewall to the upper portion ofthe second sidewall.
 18. An air in-line sensor for detecting air bubblesin a therapeutic solution flowing through a tube located in a tubeloader, the sensor comprising: a channel for receiving the tube having atube loading section; and, the tube loader having a stationary sectionand a movable section hingedly connected to the stationary section, themovable section having a blade having a radius of curvature forpositioning the tube in the tube loading section.
 19. The sensor ofclaim 18 further comprising a signal emitting member positioned on oneside of the tube and a signal receiving member positioned on an oppositeside of the tube.
 20. The sensor of claim 18 further comprising a firstlead-in section.
 21. The sensor of claim 20 wherein the first lead-insection comprises an upper portion of a first sidewall of the channel,the first lead-in section tapers upwardly and outwardly from anintermediate portion of the first sidewall to the upper portion of thefirst sidewall.
 22. The sensor of claim 20 further comprising a secondlead-in section positioned opposite the first lead-in section.
 23. Thesensor of claim 22 wherein the second lead-in section comprises an upperportion of a second sidewall of the channel, the second lead-in sectiontapers upwardly and outwardly from an intermediate portion of the secondsidewall to the upper portion of the second sidewall.
 24. An air in-linesensor for detecting air bubbles in a therapeutic solution flowingthrough a tube located in a tube loader, the sensor comprising: achannel for receiving the tube having a first lead-in section, and atube loading section; and, the tube loader having a stationary sectionand a movable section hingedly connected to the stationary section, themovable section having a blade having a radius of curvature forpositioning the tube in the tube loading section.
 25. The system ofclaim 24 further comprising a signal emitting member positioned on oneside of the tube and a signal receiving member positioned on an oppositeside of the tube.
 26. The sensor of claim 24 wherein the first lead-insection comprises an upper portion of a first sidewall of the channel,the first lead-in section tapers upwardly and outwardly from anintermediate portion of the first sidewall to the upper portion of thefirst sidewall.
 27. The sensor of claim 24 further comprising a secondlead-in section positioned opposite the first lead-in section.
 28. Thesensor of claim 27 wherein the second lead-in section comprises an upperportion of a second sidewall of the channel, the second lead-in sectiontapers upwardly and outwardly from an intermediate portion of the secondsidewall to the upper portion of the second sidewall.
 29. An air in-linesensor system for detecting air bubbles in a therapeutic solutionflowing through a tube located in a pumping mechanism, the tubeextending from a supply bag of the therapeutic solution to a patientthrough the system, the system comprising: a channel for receiving thetube having a first lead-in section, and a tube loading section; asignal emitting member positioned on one side of the tube and a signalreceiving member positioned on an opposite side of the tube; a first airbaffle positioned between the signal emitting member and the signalreceiving member; and, the tube loader having a stationary section and amovable section hingedly connected to the stationary section, themovable section having a blade having a radius of curvature forpositioning the tube in the tube loading section.
 30. The system ofclaim 29 wherein the pumping mechanism is selected from the groupconsisting of a peristaltic pump, a roller pump, an expulsor pump, afinger pump and a piston cassette pump.
 31. The sensor of claim 29wherein the first lead-in section comprises an upper portion of a firstsidewall of the channel, the first lead-in section tapers upwardly andoutwardly from an intermediate portion of the first sidewall to theupper portion of the first sidewall.
 32. The sensor of claim 29 whereinthe first air baffle prevents an ultrasonic signal from traveling aroundthe tube.
 33. The sensor of claim 29 further comprising a second airbaffle.
 34. The sensor of claim 33 wherein the second air baffle ispositioned between the signal emitting member and the signal receivingmember.
 35. The sensor of claim 34 wherein the second air baffleprevents an ultrasonic signal from traveling around the tube.
 36. Thesensor of claim 29 further comprising a second lead-in sectionpositioned opposite the first lead-in section.
 37. The sensor of claim36 wherein the second lead-in section comprises an upper portion of asecond sidewall of the channel, the second lead-in section tapersupwardly and outwardly from an intermediate portion of the secondsidewall to the upper portion of the second sidewall.
 38. An air in-linesensor for detecting air bubbles in a therapeutic solution flowingthrough a tube, the sensor comprising: means for emitting an ultrasonicsignal through the tube; means for preventing the ultrasonic signal fromtraveling around the tube; means for detecting the ultrasonic signalemitted through the tube; means for measuring the strength of theultrasonic signal emitted through the tube; means for comparing thestrength of the ultrasonic signal to a preset voltage value; means foroutputting a preset, maximum value for liquid and a preset, minimumvalue for air; and, means for determining whether to sound an airin-line alarm.
 39. The sensor of claim 38 wherein the means for emittingis a transducer.
 40. The sensor of claim 38 wherein the means forpreventing employs two air baffles positioned between a signal emittingmember and a signal receiving member.
 41. The sensor of claim 38 whereinthe means for detecting is a transducer.
 42. The sensor of claim 38wherein the means for measuring employs an electrical circuit.
 43. Thesensor of claim 38 wherein the means for comparing employs a voltagecomparator.
 44. A method for loading a tube into a channel of a medicalpump comprising the steps of: providing a tube loader having astationary section and a movable section, the movable section having ablade having a radius of curvature; positioning the tube proximate thechannel; placing the blade in contact with the tube; and, moving theblade until the tube is positioned within the tube loading section. 45.The method of claim 44 further comprising the step of providing an airsensor having a channel having a first lead-in section and a tubeloading section, and a signal emitting member positioned on one side ofthe tube and a signal receiving member positioned on an opposite side ofthe tube.